Described in DE-AS 29 50 323, which shows a species type apparatus of the type described above, is an operation aspirator wherein the suctioning tube consists of two pieces of tubing assembled over a housing, and the one tubing end, preferentially cut off diagonally,, forms a seat in the housing for the valve flap that is capable of being lifted from the seat by means of a pin penetrating the housing wall at an elastic spot. Contaminating of the aspirator tube opening by the operating person is herewith avoided. The manner in which the flexible supporting of the valve flap is arranged is technically difficult for manufacturing and the force for lifting the valve flap is relatively high, so that the hand of the operator handling the aspirator is strongly encumbered.
With a closed valve flap, the vacuum prevailing in the suctioning tube part, which is relatively great, acts upon the rear side of the valve flap and pulls it up firmly against the tubing opening. Therefore, for lifting the valve flap, the surgeon needs not only the force to overcome the resistance of the elastic, flexible support, but additionally, the vacuum prevailing on the rear side of the valve flap must be overcome so that, with actuation of the valve flap, this latter must forcefully be guided, with a "jolt", into the open position. This has operational disadvantages. In many cases, it is not desirable to always have the full vacuum available at the suctioning opening of the aspirator, rather, in certain cases of application, it is very well worth striving for that only a minimal suction force be capable of being set at the end of the suctioning tube, whereby the variation of this suctioning force should not result from valve type arrangements in the vacuum line, rather being capable of being adjusted manually by the operator in the particular case of application at hand. In other words: in the case of the known apparatus according to DE-AS 29 50 323, fine-setting by the operator himself can be carried out only with difficulty.
Generally, in the case of an aspirator of the precedingly described species, needing to be taken into account during the time in which the aspirator is not used and the suction line is closed to the outside, is that the vacuum produced by the vacuum machine inside the suction line be capable of building up in full scope, so that following some period of quiescent time of the aspirator, there prevails on the rear side of the valve flap a vacuum in the magnitude of approximately 0.8 atm. By intake of air during operation of the aspirator, normally available at the suctioning opening is a vacuum of only 0.3 atm. Hence, in the case of known aspirators, the full vacuum is effective immediately upon opening the valve which, in the case of many operations, is extremely undesirable since aspirating capacity is too great.
Finally, in the case of the aspirator according to DE-AS 29 50 323, the space in which the valve flap is acting is not accessible, i.e. corrections of a false position of the valve flap are possible only with very great difficulty. Because of the cast link connection, no positive guidance of the valve flap is guaranteed. Additionally formed, under the tubing section of the suctioning tube projecting into the valve space, is a space in which dirt particles and uncontrollable secretion residues and bone splinters can collect, which under some circumstances, can lead to faulty operation of the valve flap.
Likewise, described in U.S. Pat. No. 4,212,300 is an operation aspirator that is considered in the apparatus first above described. In the case of this known arrangement, described is a valve stem that is capable of moving against the resetting force of an elastic tension (pulling) means, said stem displaying a pass through opening that can be brought into alignment or out of alignment with the pass through opening in the housing of the actuating mechanism of the aspirator, so that opening or closing of the aspirator is therewith possible. Here, the closure process likewise results because of the elastic reset means for the valve stem, automatically upon releasing the aspirator. In the case of this known arrangement also, it is very difficult to set a fine-metering of the vacuum at the suctioning opening since, in order to achieve an absolute sealing of the valve stem in the closure position, this latter (stem) must be guided in relatively aspiration-sealed fashion inside the boring accommodating the valve stem. With actuation of the valve stem, this frictional resistance must be overcome, additionally the reset force of the elastic reset means, so that a fine-adjustment of the valve stem is not achievable with this arrangement either. Additionally, upon opening the valve, the full vacuum is active, which in many cases of operation is extremely undesirable, since aspirating capacity is too great.